Graphics calculators provide extensive information that allows for the analysis of mathematical functions and their graphs. These graphs are displayed along with related information on the calculator's display. This type of calculator also allows the user to investigate statistics, matrices, and many other mathematical processes. They can be programmed by the user to perform customized analyses. They have already had a significant impact on mathematics education on the high school and college levels.
Graphics calculators have quickly become a staple in American high schools. In their 1989 publication Curriculum and Evaluation Standards for School Mathematics, the National Council of Teachers of Mathematics recommended the incorporation of graphics calculators in all "core" high school mathematics courses. As a learning tool, the graphics calculator gives students the power to investigate mathematical patterns, improve reasoning and make original conjectures. As a teaching tool, the calculator allows the teacher to make connections to real life data, and rely less on contrived problem scenarios that could be solved easily by hand.
To adapt the graphics calculator to the instructional setting, graphics calculator manufacturers began offering viewscreens that could project the calculator's display onto a screen for classroom use. The typical calculator viewscreen is essentially the display of an associated calculator, larger in size than the display on the calculator keypad. The viewscreen is basically transparent and the data or graphics generated by the associated calculator on the viewscreen are opaque. The viewscreen thus functions as a slide or transparency when placed on the lighted surface of an overhead projector and the data or graphics are projected onto the screen. An example of such a calculator viewscreen is the viewscreen manufactured for the Texas Instruments Model TI-82 graphics calculator.
In typical classroom usage, the instructor must first set up the overhead projector on a desk or other surface, then place the calculator viewscreen on the projector and connect the various A.C. line cords to power outlets and the calculator keypad unit to the viewscreen. At the conclusion of the lesson, the various units must be disassembled and moved to another classroom or into storage areas. This excessive movement infringes on class time. Teachers may not truly integrate the calculator into appropriate daily class activities because of the set-up and break-down time required. The frequent set-up and breakdown also makes the expensive equipment susceptible to damage. The fragility of the viewscreen and its cost require that it must be safely stored away when not in use. Consequently, it is difficult to fully utilize the capabilities of the viewscreen in classroom activities.
To avoid distortion, the plane of the screen on which the image from an overhead projector is projected should be perpendicular to the direction of projection. This is especially important when presenting graphical representations from a graphics calculator. Conventionally, in the classroom, the overhead projector is put on a desk and the calculator viewscreen positioned on the lighted plate of the projector. The projection screen is usually of the "window-shade" type that pulls down over the chalkboard at the front of the room. The combined bulk of the overhead projector and the calculator viewscreen often blocks the view of the image for many students in the classroom. Simply raising the projection screen yields a distorted graph that is partially out of focus. Even when the projection screen is not in use, view of the chalkboard is impeded by the overhead projector and calculator viewscreen, which then must be removed and placed somewhere else. The necessary movement of the fragile viewscreen and projector, with their trailing electrical cords can lead to accidents. Consequently, shifting from boardwork to the calculator display, the quintessence of integration of these materials, becomes cumbersome and distracting.
It is therefore desirable to provide a piece of equipment that will facilitate the easy, frequent and shared use of a calculator viewscreen and overhead projector by minimizing or eliminating the problems associated with their use.